Answer:
A. pivot rightward (pivot out) along the horizontal axis
Explanation:
Tea and coffee represent substitute goods. If price of a good increases, this causes an increase in quantity demanded of it's substitute.
In the given case, quantity demanded of tea is measured on horizontal axis while quantity demanded of coffee is measured on vertical axis. The budget constraint for tea and coffee shows different combinations of quantity of tea and coffee demanded within a fixed expenditure.
When price of coffee increases, within the same budget constraint, the quantity demanded of tea shall rise.
This would lead to the budget constraint to pivot rightward (pivot out) along the horizontal axis.
